Latch mechanism

ABSTRACT

A system for latching the access door of a rotatable apparatus includes a normally disengaged rotation sensor operatively connected to a door latch mechanism. The rotation sensor is actuated to a sensing condition by a latch mechanism responsive to an attempt to open the door and in turn controls the latch mechanism to prevent opening of the door when the rotatable apparatus is rotating. The latch mechanism includes a pivotally mounted assembly movable as a unit when there is no rotation to permit opening of the door. A latch pawl included in the assembly is separately and pivotally movable responsive to the sensing of rotation to prevent opening of the door.

iJnited States Patent [191 Nelson May 22,1973

[54] LATCH MECHANISM [75] Inventor: Robert B. Nelson, Newton, Iowa [73] Assignee: The Maytag Company, Newton,

Iowa

[22] Filed: Oct. 20, 1971 [21] App1.No.: 190,775

[52] U.S. Cl. ..210/146, 192/136, 229/201 [51] Int. Cl. ..B04b 7/06 [58] Field of Search ..2l0/146; 192/136;

[56] References Cited UNITED STATES PATENTS 1,417,430 5/1922 Tulloch et a1. ..292/20l 2,910,317 10/1959 Conlee ..292/201 X 3,539,011 11/1970 Hopkins ..2l0/146 2,902,850 9/1959 Sheffer ..192/l36 X Primary Examiner-Samih N. Zaharna Assistant Examiner-F. F. Calvetti Attorney-William G. Landwier et al.

[57] ABSTRACT A system for latching the access door of a rotatable apparatus includes a normally disengaged rotation sensor operatively connected to a door latch mechanism. The rotation sensor is actuated to a sensing condition by a latch mechanism responsive to an attempt to open the door and in turn controls the latch mechanism to prevent opening of the door when the rotatable apparatus is rotating. The latch mechanism includes a pivotally mounted assembly movable as a unit when there is no rotation to permit opening of the door. A latch pawl included in the assembly is separately and pivotally movable responsive to the sensing of rotation to prevent opening of the door.

12 Claims, 1 1 Drawing Figures LATCH MECHANISM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a latch mechanism and more particularly to a latch mechanism cooperatively attached to a rotation sensor device and selectively actuatable to a latching condition or a non-latching condition.

2. Description of the Prior Art The prior art shows a continuing search for a control system for a rotating apparatus, such as a laundry appliance, to insure safe operation of the apparatus. Previous work in the appliance field also shows it to be desirable to prevent access to the fabric container of a centrifugally operable washing machine during the extraction operation. Early systems for achieving this desired objective disclose switching means responsive to the opening of the access door for de-energizing the drive system so that the container is not driven while the access door is in the open position. Also shown in prior art are control systems including solenoid or relay operated lid switches controlled by program control means so that the solenoid or relay is energized for locking the access door upon energization of the drive system for the extraction operation to avoid or prevent access to the spinning container.

It has, more recently, been recognized that in some constructions a container continues to spin for a significant period of time after'de-energization of the drive system and therefore time delay mechanisms have been added to the system in an attempt to insure that the rotatable container has been given an opportunity to stop or at least greatly decrease in speed prior to unlocking the access door. In even more recent developments, as in a copending application, Ser. No. 190,774, filed on an even date with this application by William G. Landwier, entitled Motion Sensing Latch System, and assigned to the assignee of the instant invention, a rotation sensitive latch system positively insures non-access to the container while it is rotating by providing cooperatively connected rotation sensing means and lid latching mechanism. The direct connection between the rotation sensor and the latch mechanism, however, brings with it unique problems solved by the-instant invention which is also disclosed in the copending application.

SUMMARY OF THE INVENTION It is therefore an object of the instant invention to provide an improved latch mechanism selectively responsive to rotation sensing means for establishing a door latching condition or a non-latching condition.

It is a further object of the instant invention to provide an improved latch mechanism operable for positively latching the door of a rotatable apparatus in a locked condition responsive to an attempt to open the door and to rotation of the apparatus and movable to a non-latching condition responsive to an attempt to open the door in the absence of rotation to permit relatively unrestricted movement of the door to the open position.

It is a further object of the instant invention to provide an improved latch mechanism including a movably mounted member operatively connected to rotation sensing means and further including a latch pawl yieldingly connected to the movably mounted member and operable between latching and non-latching conditions.

The instant invention achieves these objects in a latch mechanism including a first movably mounted member operatively connected to the rotation sensing device and further including a second member mounted on the movably mounted member for movement therewith or movement relative thereto responsive to a condition of rotation as sensed by the rotation sensor.

Operation of the device and further objects and advantages thereof will become evident as the description proceeds and from an examination of the accompanying four pages of drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings illustrate a preferred embodiment of the invention with similar numerals referring to similar parts throughout the several views wherein:

FIG. 1 is an overall view of an automatic washing machine with various components broken away to show portions of the door latching system incorporating the instant invention;

FIG. 2 is a fragmentary sectional view of the latch mechanism of the instant invention as taken generally along section line 22 of FIG. 3 and section line 22 of FIG. 4;

FIG. 3 is a fragmentary sectional view showing a generally plan view of a portion of the latch mechanism as taken along section line 33 of FIG. 2;

FIG. 4 is a sectional view of the door mounted latch mechanism as taken along section line 4-4 of FIG. 2;

FIG. 5 is a generally end view of a portion of the latch mechanism as taken along section line 5-5 of FIG. 3;

FIG. 6 is a view including in sectional form the rotation sensing device of the door latching system of the instant invention;

FIG. 7 is a view of the latch mechanism of the instant invention similar to FIG. 2 and showing the nonlatching operation of the latch mechanism;

FIG. 8 is a view of the rotation sensing device as taken along line 8-8 of FIG. 6 and is similar to the section view of FIG. 6 showing operation of the sensor in the absence of rotation of the fabric container;

FIG. 9 is similar to FIGS. 2 and 7 and shows a further view of the door latching mechanism in the doorlatching position;

FIG. 10 is a view of the rotation sensing device similar to FIG. 8 and shows operation of the rotation sensing device in the presence of rotation of the fabric container; and

FIG. 11 is a view of the door latching system as shown in FIGS. 2, 7 and 9 and shows operation of the latch mechanism during the closing operation of the access door.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 there is shown an automatic washing machine including a base frame 10 supported on a plurality of adjustable legs 11 and mounting a cabinet comprising a sidewall 13 and a top cover 14. The top cover 14 includes a hinged panel comprising an access door 15 normally covering a recessed loading opening 16 and movable to an open position to permit access through the opening 16. The top cover 14 further includes an upwardly extending housing 19 for accommodating various control members such as Mounted within the cabinet is a tub assembly 21 nutationally supported on the base frame by" an inverted tripod arrangement including tub braces 23 which are connected at the lower end to a support member 24 positioned on the base frame 10. The tub braces 23 are connected at their upper ends to a generally imperforate outer liquid container or tub 25. The tub braces 23 are also resiliently connected to the base frame 10 by means of centering springs 26 which resist rotation of the support member 24 relative to the base frame 10 but permit nutational movement relative to the base frame 10.

Revolubly mounted in the imperforate outer tub 25 is a perforate clothes basket or fabric container 28 in which is positioned an oscillatable agitator 29 for effecting movement of the fabrics and washing fluid within the tub assembly 21. The imperforate outer tub 25 and the perforate inner fabric container 28 are substantially aligned with the loading opening 16 in the top cover 14 for permitting the operator to place articles within the fabric container 28 and remove them upon completion of the cycle.

The base frame 10 also supports through motor mount 30 a reversible drive motor 31 operable in a bidirectional drive system for selectivelyeffecting oscillation of the agitator 29 or centrifugal rotation of the inner fabric container 28. The drive system for effecting operation of the agitator and rotation of the fabric container includes a double groove pulley 33 fixed to the shaft of the motor 31 and drivingly engaged with a main drive belt 34 which in turn is drivingly engaged with the main drive pulley 35. The main drive pulley 35 is drivingly connected to either the agitator 29 through a drive shaft (not shown) and the gearing of a transmission 36 or to the fabric container 28 through the housing of the transmission 36 and a clutch (not shown). Operation of the motor 31 in a first direction effects rotation of the main drive pulley 35 for effecting oscillation of the agitator 29 through the drive shaft (not shown) and transmission gearing while operation of the motor 31 in the opposite direction effects rotation of the drive pulley 35 and the transmission 36 through the clutch (not shown) for rotating the inner tub 28 to effect centrifugal extraction of liquid.

The base frame 10 also supports pumping means 39 driven by the bidirectional motor 31 through the motor mounted pulley 33, the pump drive belt 40 and the pump mounted pulley 41. The pump 39 communicates with the outer tub 25 through the conduit 43 and is operable for pumping liquids from the outer tub 25 toward an external drain when the motor 31 is operated in the direction for effecting centrifugal rotation of the inner tub 28. Since the pump 39 is drivingly connected to the bidirectional motor 31 and is operable in the first and second directions with the motor, the pump 39 will tend to pump liquid toward the outer tub 25 through the conduit 43 when the motor 31 is operating in the direction for effecting agitation of the fabrics during the washing portion of the cycle.

The washing machine is provided with controls for programming the machine through a sequence of operations including energization of the motor 31 for operation in a first direction to effect a washing and/or rinsing function followed by energization of the motor 31' in a second direction to effect a liquid extraction function.

Though not shown, the appliance is provided with means for braking the rotation of the container 28 upon deenergization of the motor 31. During this braking or deceleration period the rotating container 28 is effectively operable as a driving member because of the rotating mass and tends to continue rotation for a few seconds and to effect rotation of the motor 31 and the pump 39 as long as rotation of the container 28 continues.

The construction and mounting of the tub assembly and the operation of the fabric container 28 and agitator 29 are more clearly and specifically shown in the following patents, each of which is assigned to the assignee of the instant invention: Scott et al., US. Pat. No. 2,854,297; Smith et al, US. Pat. No. 2,926,136; Burkland, US. Pat. No. Re. 25,157; and Goodlaxson, US. Pat. No. 3,013,645.

The latch mechanism for latching the access door 15 in the closed position relative to the cabinet top cover 14 is referred to generally as numeral 45 in FIG. 2 and includes an access door mounted portion 46 and a top cover mounted portion 47. The door mounted portion 46 comprises a housing member 49 which, as in FIG. 4, is secured by a pair of screws 50 and provides a keyed slot 51 for slidably supporting a latch member 53. In FIG. 4 the spacing between the housing member 49 and latch member 53 is exaggerated for clarity. The latch member 53 includes a lower finger portion 54 extending beyond the edge of the door 15 as in FIG. 2. A leaf spring 55 biases the latch member 53 toward the left as in FIG. 2 for engagement with the top cover mounted latch mechanism portion 47.

A latch support member secured to the top cover 14 includes, as in FIG. 3, a first portion 61 secured to the top cover 14 by a pair of screws 63 and a second portion 64 extending at a right angle to the first portion 61 and engageable with a flange 65 of the top cover 14 for support of the left end of the right angle portion 64. The right angle portion 64 of the latch support member 60 includes a cable groove 66 as best shown in FIGS. 3 and 5 for receiving a cable 69.

The first portion 61 of the cabinet mounted support member 60 pivotally supports a shaft 70 having a pivot portion extending longitudinally through the first portion 61 of the support member 60 and further includes a double D shaped portion 71 at one end, as viewed in FIG. 3, and an offset flange 73 at the otherjend serving as a crank arm forthe shaft 70. The cablej69 is operatively connected to the crank arm through the cable eyelet 74 and-the hook.7;5 on the flange 7,3.

' the shaft 70 for pivot action therewith. The pivot mem- The top cover mounted latch mechanism47' further includes a pivot member 76 mounted on the shaft 70 at the double D portion 71 and is operatively fixed to ber 76 further includes an arm portion 79, as in FIG. 2, extending toward the left and terminating in a pivot element 80. The pivot element 80 is engageable with a corresponding groove 81 in a latch pawl 83 for pivotally supporting the latch pawl 83 on the pivot member 76. The latch pawl 83 includes a projecting portion 84, extenting to the right in FIG. 2, for engagement with the extending finger 54 of the door mounted latch member 53. The extending portion 84 of the latch pawl 83 assume's'an overlapping relationship with the latch finger '54 for engagement thereby upon an attempted opening of the door 15. The latch pawl 83 also includes an upwardly extending shoulder 85 engageable with one side 86 of a fixed abutment 89 to limit counterclockwise movement of the latch pawl 83 and pivot member 76 about the axis of the shaft 70 under certain conditions. A step 90 on the latch pawl 83 engages the other side 91 of the abutment 89 to limit clockwise movement and locate the latch pawl 83 and pivot member 76 assembly.

A pinch spring 93 is engageable with the upper side of the latch pawl 83 and the lower side of the pivot element 76 to biasingly maintain the two members in contact with each other and provide an assembly, indicated generally as numeral 92 in the drawings, operable as a unit with the shaft 70, at least initially, when a rotating force is applied to the assembly 92 such as when an attempt is made to open the door 15.

The assembly 92 of pivot member 76 and latch pawl 83 are effectively biased to the position shown in FIG. 2 with the step 90 engaging the abutment 89 by connection through the cable 69. The cable 69 extends from the crank arm flange 73 of the shaft 70 over the cable groove 66 and downwardly for connection to a pivot arm 94 of a rotation sensing device 95 as shown generally in FIG. 1 and more specifically in FIGS. 6, 8, and 10.

As indicated in FIG. 6 and better shown in the section views of FIGS. 8 and the rotation sensing device 95 includes a generally cylindrical housing 96 fixed to the pump housing 99 with a pair of screws 100. The housing 96 supports a cylinder 101 for downward axial movement relative thereto by urging of the inner end 103 of the pivot arm 94. The cable 69 is adjustably connected to the outermost end of the pivot arm 94 to facilitate the proper positioning of the door latch mechanism assembly 92 and the rotation sensing device 95. It is observed that as an upward force or pull is applied to the cable 69 the pivot arm 94 is operable about a pivot 104 to move the inner portion 103 of the arm 94 in a downwardly direction to move the cylinder 101 toward the pump pulley 41. A coil spring 105 is disposed between the housing 96 and the cylinder 101 to resist downward movement of the cylinder 101 and to return the cylinder 101 when the cable 69 is released.

Disposed within the movable cylinder 101 is a probe or plunger 106 including a lower portion 109 extending downwardly to adjacent the pump pulley 41 and further including an annular shoulder 110 and an upper portion 111 disposed within the cylinder 101. A second spring 113 is disposed within the cylinder 101 encircling the upper portion 111 of the plunger 106 and en gaging one side of the shoulder 110 to generally maintain the plunger 106 centered and biased downwardly with the other side of the shoulder 110 engaging the end cap 114 of the movable cylinder 101.

During the initial movement of the cylinder 101 responsive to an upward pull on the cable 69 the plunger 106 will move downwardly into engagement with the pulley 41 and, with the pulley 41 at rest, will then move relative to the cylinder 101 into the recess 115 within the cylinder 101 as in FIG. 8. If, however, the pump pulley 41 is rotating the plunger 106 will pivot relative to the cylinder 101 at the shoulder 110 so that the upper end 1 13 of the plunger 106 will engage an abutment 116 disposed within the cylinder 101 as in FIG. 10 and prevent further movement of the plunger 106 relative to the cylinder 101.

Further explanation hereinbelow of the operation of the rotation sensing device with the lid latch mechanism will clearly show the achieving of the desired parameters for a rotation sensitive door latch mechanism as previously indicated to include: (1) a sensor that does not produce a drag on the drive system or driven members with the lid in the closed position; (2) a door latch mechanism that does not interfere with door movement when no rotation is present; and (3) a door latch system that prevents movement of the door from the closed position while the fabric container is rotating. The accomplishing of these parameters will be shown by the further explanation of the operation of a rotation sensitive door latch mechanism comprising the instant invention.

- Under normal conditions, as previously shown in FIG. 6, the rotation sensing device is disengaged from the rotating system by virtue of the spacing between the pump pulley 41 and the plunger 106. It is only upon an attempt to open the access door 15 when the machine is rotating that the plunger 106 will move into engagement with the pulley 41. Referring to FIGS. 7 and 8 the operation of the door latch and rotation sensing system is shown when the access door 15 is moved from the closed position while no rotation of the fabric container is present. Referring specifically to FIG. 7, the initial opening movement of the door 15 applies a force through the extending finger 54 to the extending portion 84 of the latch pawl 83 and in the absence of restraint applied to the shaft 70, as will be shown, the latch pawl 83 and pivot member 76 pivot as a unit with the shaft about the axis of the shaft 70. The shoulder misses abutment 89 so that the extending portion 84 is retracted into the top cover 15. In the continued absence of the restraint on the shaft 70, indicating the absence of rotation of the container 28, the pawl 83 and pivot member 76 will thus pivot to permit continued movement of the door 15 from the closed position toward the open position.

Referring more specifically to FIG. 8 and also reviewing the crank arrangement shown in FIG. 5 it is seen that the counterclockwise movement of the assembly 92 of latch pawl 83 and pivot member 76 about the axis of the shaft 70 produces a pull on the cable 69 which moves the pivot arm 94 relative to the sensor device housing 96 to effect a downward movement of the cylinder 101 so that the plunger 106 engages the pulley 41. In the absence of rotation of the pulley 41 the pull on the cable 69 is permitted to move the cylinder 101 downwardly relative to the plunger 106 and thus enables the assembly 92 of latch pawl 83 and pivot member 76 to move to the retracted position as explained relative to the showing of FIG. 7. Thus with no restraint produced on the shaft 70 the pivoting of the cabinet mounted latch assembly 92 permits the opening of the access door 15.

If, however, an attempt is made to move the access door 15 from the closed position while the container 28 is rotating, the operation of the latch and sensor mechanisms is quite different. Referring to FIGS. 9 and 10, the initial movement of the door 15 from the closed position again produces a force on the extended portion 84 of the latch pawl 83 and moves the assembly 92 of latch pawl 83 and the pivot member 76 a short distance about the axis of the shaft 70 to produce a pull on the cable 69 and a small downward movement of the sensor cylinder 101 and plunger 106 to effect engagement of the plunger tip 109 with the surface of pulley 41. Since the pulley 41 is moving as indicated by the arrow 119 in FIG. 10, the plunger 106 is immediately tilted relative to the cylinder 101 so that the uppermost portion 111 of the plunger 106 is engageable with the in- I ternal abutment 116 of the cylinder 101. The plunger 106 will thus not permit further movement of the cylinder 101 so that the pivot arm 94 is locked and the cable 69 effectively restrains the shaft 70 and assembly 92 from further pivotal movement.

Upon encountering a shaft 70 restrained from further pivotal movement, the attempted opening of the access door 15 will produce a force on the extended portion 84 of the latch pawl 83 to move the latch pawl 83 relative to the pivot member 76 against the biasing of the pinch spring 93. The latch pawl 83, however, includes a shoulder 85 engageable with the abutment 89 to prevent further movement of the latch pawl 83. Further movement of components in the latch mechanism and sensor device is prohibited and because of the overlapping relationship of the latch pawl 83 and the lid mounted latch member 53, movement of the door from the closed position is prohibited.

It is noted that an important feature of this invention is the pivotal mounting of the latch pawl 83 on the pivot member 76 so that, upon the locking of the sensor in the presence of rotation, undue loading on the connection between the lid latch and the rotation sensor is avoided. If the latch pawl 83 and pivot member 76 were formed as a unitary member and directly connected to the rotation sensor there would be excessive loading and stress placed on the cable and on the rotation sensor as an attempt was made to force open the lid in the presence of rotation. It is thus clear in the instant invention that when the shaft is held immobile by the cable, the spring loaded latch pawl is lifted by the lid mounted latch member 53 into engagement with the abutment 89 to limit transmission of force from the lid 15 to the remainder of the system.

The attempt to open the door 15 is thus blocked and, upon release of the door 15 by the operator, the latch assembly 92 returns to the normal position as shown in FIG. 2. The cable 69 is relaxed so that the plunger 106- and cylinder 101 are returned to the normal position as in F IG. 6 with the plunger 106 disengaged from the pulley 41 so that rotation of the container is without drag or interference by the sensing system.

Once the rotation has ceased the door 15 may be easily and conveniently moved to the open position as shown in FIG. 7 to permit access to the fabric container 28. The door 15 is also conveniently moved from the open position to the closed position as shown in'FIG. 11 wherein the lid-mounted latch element 53 is shown as being cammed or moved to the right as the extending finger 54 moves downwardly on the upper surface 120 of the extending portion 84 of the latch pawl 83. The pivot element 76 also includes a resilient cushion member 121 for absorbing the impact of the lid-mounted latch member 53 as it returns under a spring loaded force to its normal position as shown in FIG. 2.

The sensor device 95 shown in FIGS. 6, 8 and 10 includes an internal abutment 116 or shoulder on only one internal side of the cylinder 101. The device is thus unidirectionally responsive to the drive system. The system can, however, be made bidirectionally responsive by providing a shoulder on both sides of the internal bore and non-directional by providing an annular shoulder within the cylinder 101.

The sensing probe or plunger 106 is shown as engageable with the pump pulley 41 but may also be mounted for sensing movements of other portions of the drive system or with the driven container itself as a positive indication of rotation of the container.

The instant invention therefore offers clear and distinct advantages over access door latch mechanisms shown in the prior art. The door latch mechanism achieves secure locking of the door without undue interference or resistance to door movement when there is no rotation. The door latch mechanism also achieves a direct connection with the rotation sensor while obviating undue operational loading and wear on the components.

In the claims and specification there has been set forth a preferred embodiment of the invention and although specific terms are employed these are used in a generic and descriptive sense only and not for purposes of limitation. Changes in form and the proportion of parts as well as the substitution of equivalents are contemplated as circumstances may suggest or render expedient without departing from the spirit or scope of this invention as defined in the following claims.

I Claim:

1. A latch mechanism for an apparatus having cabinet means and an access door on said cabinet means operable between a generally closed position and an open position, the combination comprising: first latch means on said access door; second latch means mounted on said cabinet means comprising-a latch member mounted for movement relative to said cabinet means and a latch pawl yieldingly mounted on said latch member, said latch pawl including an extended latch portion engageable with said first latch means for preventing movement of said access door to said open position under a predetermined condition and being movable with said latch member from a first posture to a nonlatching posture to retract said latch portion and permit movement of said access door from said closed position toward said open position in the absence of said predetermined condition; and stop means engageable by said latch pawl, said latch pawl being movable relative to said latch member and against said stop means to a door latching posture responsive to said predetermined condition for preventing movement of said access door to said open position.

2. A latch mechanism as defined in claim 1 wherein said second latch means includes means for biasing said latch pawl to a predetermined position relative to said latch member and operable for effecting movement of said latch member and said latch pawl together in the absence of said predetermined condition and for yieldingly opposing movement of said latch pawl relative to said latch member toward said door latching posture in the presence of said predetermined condition.

3. A latch mechanism for an apparatus having cabinet means and an access door on said cabinet means operable between a generally closed position and an open position, the combination comprising: first latch means on said access door; second latch means mounted on said cabinet means and including a shaft pivotally mounted on said cabinet means, a pivot member mounted on said shaft for movement therewith, a latch pawl including an extended portion engageable with said first latch means and pivotally mounted on said pivot member for movement relative thereto, said latch pawl being movable with said pivot member from a first posture to a non-latching posture to retract said latch pawl and permit movement of said access door toward said open position; and stop means engageable by said latch pawl, said latch pawl under a predetermined condition being also movable relative to said pivot member and against said stop means to a doorlatching posture for preventing movement of said access door to said open position.

4. A latch mechanism as defined in claim 3 wherein said second latch means includes first means for biasing said latch pawl relative to said pivot member for engagement by said first latch means and further includes second means for biasing said second latch means into position for engagement by said first latch means.

5. A latch mechanism as defined in claim 3 wherein said first latch means includes a movable member biased to a position underlying said extended portion for engagement therewith upon an attempt to move said access door from said closed position and wherein said movable member is cammed to a second position to permit movement of said access door from said open position to said closed position.

6. A latch mechanism for an apparatus having cabinet means and an access door on said cabinet means operable between a generally closed position and an open position, the combination comprising: first latch means on said access door; second latch means mounted on said cabinet means and cooperable with said first latch means to selectively lock said access door in said closed position, said second latch means including a shaft pivotally mounted on said cabinet means, a pivot member mounted on said shaft for movement therewith, a latch pawl pivotally mounted on said pivot member for movement relative thereto and having an extended portion for engagement with said first latch means, and means for biasing said latch pawl relative to said pivot member; means for selectively restraining movement of said shaft responsive to a condition of said apparatus, said second latch means being pivotable with said shaft to retract said extended portion and permit movement of said access door from said closed position to said open position in the absence of said condition of the apparatus; and stop means engageable by said latch pawl, said latch pawl being movable relative to said pivot member and against said stop means responsive to initial movement of said access door from said closed position when movement of said shaft is restrained for preventing movement of said access door to said open position.

7. A latch mechanism as defined in claim 6 wherein means including second biasing means is operable for locating said second latch means in a generally predetermined position relative to said cabinet means for engagement of said first latch means with said extended portion.

8. A latch mechanism as defined in claim 6 wherein said first latch means includes a movable member biased to a predetermined position on said access door for engagement with said extended portion and wherein said movable member is cammed from said predetermined position by said extended portion for permitting movement of said access door from said open to said closed position.

9. A latch mechanism as defined in claim 8 and further including energy-absorbing cushion means engageable with the movable member of the first latch means upon movement of said access door to the closed position.

10. In an apparatus including a rotatable member, the combination comprising: cabinet means substantially enclosing said rotatable member; an access door on said cabinet means operable between a generally closed position and an open position; first latch means on said access door; second latch means movably mounted on said cabinet means and cooperable with said first latch means to selectively lock said access door in said closed position, said second latch means including a movably mounted latch member, a latch pawl yieldingly mounted on said latch member for movement relative thereto and extending from said cabinet means for engagement with said first latch means, and means for biasing said latch pawl relative to said latch member; rotation sensing control means operatively connected to said latch member for permitting movement thereof in the absence of rotation of said rotatable member and to limit movement thereof in the presence of rotation of said rotatable member, said second latch means being movable in the absence of rotation to retract said latch pawl and permit movement of said access door toward said open position; and stop means on said cabinet means engageable by said latch pawl, said latch pawl being movable relative to said latch member and against said stop means when the presence of rotation of said rotatable member limits movement of said latch member for preventing movement of said access door to said open position.

11. In an apparatus as defined in claim 10 wherein movement of said second latch means is produced by the initial attempted movement of said access door from said closed position.

12. In an apparatus as defined in claim 10 wherein said biasing means is operable between said latch member and said latch pawl to effect unitary movement of said latch pawl and latch member when said latch member is free for movement and to permit movement of said latch pawl relative to said latch member when said latch member is restrained to effectively prevent overloading of said latch member and said rotation sensing control means while maintaining the access door latched.

l l i 

1. A latch mechanism for an apparatus having cabinet means and an access door on said cabinet means operable between a generally closed position and an open position, the combination comprising: first latch means on said access door; second latch means mounted on said cabinet means comprising a latch member mounted for movement relative to said cabinet means and a latch pawl yieldingly mounted on said latch member, said latch pawl including an extended latch portion engageable with said first latch means for preventing movement of said access door to said open position under a predetermined condition and being movable with said latch member from a first posture to a nonlatching posture to retract said latch portion and permit movement of said access door from said closed position toward said open position in the absence of said predetermined condition; and stop means engageable by said latch pawl, said latch pawl being movable relative to said latch member and against said stop means to a door latching posture responsive to said predetermined condition for preventing movement of said access door to said open position.
 2. A latch mechanism as defined in claim 1 wherein said second latch means includes means for biasing said latch pawl to a predetermined position relative to said latch member and operable for effecting movement of said latch member and said latch pawl together in the absence of said predetermined condition and for yieldingly opposing movement of said latch pawl relative to said latch member toward said door latching posture in the presence of said predetermined condition.
 3. A latch mechanism for an apparatus having cabinet means and an access door on said cabinet means operable between a generally closed position and an open position, the combination comprising: first latch means on Said access door; second latch means mounted on said cabinet means and including a shaft pivotally mounted on said cabinet means, a pivot member mounted on said shaft for movement therewith, a latch pawl including an extended portion engageable with said first latch means and pivotally mounted on said pivot member for movement relative thereto, said latch pawl being movable with said pivot member from a first posture to a non-latching posture to retract said latch pawl and permit movement of said access door toward said open position; and stop means engageable by said latch pawl, said latch pawl under a predetermined condition being also movable relative to said pivot member and against said stop means to a door-latching posture for preventing movement of said access door to said open position.
 4. A latch mechanism as defined in claim 3 wherein said second latch means includes first means for biasing said latch pawl relative to said pivot member for engagement by said first latch means and further includes second means for biasing said second latch means into position for engagement by said first latch means.
 5. A latch mechanism as defined in claim 3 wherein said first latch means includes a movable member biased to a position underlying said extended portion for engagement therewith upon an attempt to move said access door from said closed position and wherein said movable member is cammed to a second position to permit movement of said access door from said open position to said closed position.
 6. A latch mechanism for an apparatus having cabinet means and an access door on said cabinet means operable between a generally closed position and an open position, the combination comprising: first latch means on said access door; second latch means mounted on said cabinet means and cooperable with said first latch means to selectively lock said access door in said closed position, said second latch means including a shaft pivotally mounted on said cabinet means, a pivot member mounted on said shaft for movement therewith, a latch pawl pivotally mounted on said pivot member for movement relative thereto and having an extended portion for engagement with said first latch means, and means for biasing said latch pawl relative to said pivot member; means for selectively restraining movement of said shaft responsive to a condition of said apparatus, said second latch means being pivotable with said shaft to retract said extended portion and permit movement of said access door from said closed position to said open position in the absence of said condition of the apparatus; and stop means engageable by said latch pawl, said latch pawl being movable relative to said pivot member and against said stop means responsive to initial movement of said access door from said closed position when movement of said shaft is restrained for preventing movement of said access door to said open position.
 7. A latch mechanism as defined in claim 6 wherein means including second biasing means is operable for locating said second latch means in a generally predetermined position relative to said cabinet means for engagement of said first latch means with said extended portion.
 8. A latch mechanism as defined in claim 6 wherein said first latch means includes a movable member biased to a predetermined position on said access door for engagement with said extended portion and wherein said movable member is cammed from said predetermined position by said extended portion for permitting movement of said access door from said open to said closed position.
 9. A latch mechanism as defined in claim 8 and further including energy-absorbing cushion means engageable with the movable member of the first latch means upon movement of said access door to the closed position.
 10. In an apparatus including a rotatable member, the combination comprising: cabinet means substantially enclosing said rotatable member; an access door on said cabinet means operable between a generally closed position and an open Position; first latch means on said access door; second latch means movably mounted on said cabinet means and cooperable with said first latch means to selectively lock said access door in said closed position, said second latch means including a movably mounted latch member, a latch pawl yieldingly mounted on said latch member for movement relative thereto and extending from said cabinet means for engagement with said first latch means, and means for biasing said latch pawl relative to said latch member; rotation sensing control means operatively connected to said latch member for permitting movement thereof in the absence of rotation of said rotatable member and to limit movement thereof in the presence of rotation of said rotatable member, said second latch means being movable in the absence of rotation to retract said latch pawl and permit movement of said access door toward said open position; and stop means on said cabinet means engageable by said latch pawl, said latch pawl being movable relative to said latch member and against said stop means when the presence of rotation of said rotatable member limits movement of said latch member for preventing movement of said access door to said open position.
 11. In an apparatus as defined in claim 10 wherein movement of said second latch means is produced by the initial attempted movement of said access door from said closed position.
 12. In an apparatus as defined in claim 10 wherein said biasing means is operable between said latch member and said latch pawl to effect unitary movement of said latch pawl and latch member when said latch member is free for movement and to permit movement of said latch pawl relative to said latch member when said latch member is restrained to effectively prevent overloading of said latch member and said rotation sensing control means while maintaining the access door latched. 